The invention relates to a sheet-metal fastener or nut comprising a sheet-metal member having a central stamped and apertured portion forming a protuberance which is shaped to define an internal screw thread.
The invention in particular applies to sheet-metal nuts bent to a U-shape and adapted to slip over and clamp to the edge of a support base, provided with holes for receiving fasteners, for instance screws.
In that case, a screw is inserted through and against an aperture in the lower leg of the U-shaped nut and is pushed through aligned holes in support bases to be connected as far as the vicinity of the stamped portion thread. Using a simple tool, such as a screwdriver, the screw is rotated to threadedly engage the thread in the central stamped portion. Continued threading action of the screw draws the support bases gradually toward each other until ultimately they are compressed and fastened together. This is a lasting and secure connection, provided it be free from vibrations or impacts.
However such vibrations and impacts are unavoidable, for example, in a motor vehicle moving over uneven surfaces of a road. In such case the resulting vibrations cause loosening of the fastener because the thread is not selflocking. The screw then gradually backs out of this thread and the fastener connection ultimately is lost.